Hi Jens,

Unfortunately I couldn't find it locally anymore and Bitbucket's Mercurial 
repos aren't accessible anymore. There should be a copy somewhere (probably 
Gaël has one in the pull request archive), I'll look around.

David

> On 8. Oct 2020, at 23:11, Jens Wehner <[email protected]> wrote:
> 
> Hey David,
> 
> have you found the code?
> 
> I like the Hermitian matrix for the memory saving and for very nicely 
> expressing physics in the datatype. I think the idea was to put it into the 
> unsupported.
> 
> Cheers Jens
> 
> | Jens Wehner, PhD | eScience Research Engineer | Email: 
> [email protected] 
> <https://outlook.office.com/mail/options/mail/[email protected]> | 
> Tel: +31(0)6 438 666 87 |
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> 
> 
> From: David Tellenbach <[email protected]>
> Sent: Tuesday, October 6, 2020 20:36
> To: [email protected] <[email protected]>
> Subject: Re: [eigen] Hermitian matrices
>  
> @Rasmus, here are some benchmarks: 
> https://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2018/08/msg00010.html
>  
> <https://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2018/08/msg00010.html>
>  (scroll the the very end). As already said, Hermitian * Hermitian can give 
> quite good performance and Dense * Hermitian doesn't really hurt. 
> 
>> On 6. Oct 2020, at 02:26, David Tellenbach <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> IIRC it was in fact you who suggested using not a plain packed but a 
>> rectangular full packed format ;-) 
>> (https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-c/top/lapack-routines/matrix-storage-schemes-for-lapack-routines.html#matrix-storage-schemes-for-lapack-routines_RFP_STORAGE
>>  
>> <https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-c/top/lapack-routines/matrix-storage-schemes-for-lapack-routines.html#matrix-storage-schemes-for-lapack-routines_RFP_STORAGE>)
>> 
>> If this is worth definitely depends on the particular use-case. It has been 
>> shown that a rectangular full packed format can be beneficial for e.g. 
>> Cholesky (http://www.netlib.org/lapack/lawnspdf/lawn199.pdf 
>> <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.214.102&rep=rep1&type=pdf>)
>>  or Pade approximations 
>> (https://pdfs.semanticscholar.org/86d2/28da4fc02672b2c990eb48a5a605c0e0360f.pdf
>>  
>> <https://pdfs.semanticscholar.org/86d2/28da4fc02672b2c990eb48a5a605c0e0360f.pdf>).
>>  I published benchmark on this list and will try to dig them out. A 
>> Hermitian*Hermitian product can be quite fast (you can basically fall back 
>> to gemm for blocks in the RFP format) but Dense*Hermitian was not so good if 
>> I remember correctly.
>> 
>> David
>> 
>>> On 6. Oct 2020, at 02:16, Rasmus Munk Larsen <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> David,
>>> 
>>> I can see that this might save 50% of memory by only storing the upper or 
>>> lower triangle, and it would be nice to be able to automatically dispatch 
>>> to faster eigensolvers etc. for Hermitian matrices. However, packed storage 
>>> kernels are notoriously hard to optimize, and I wonder how much we would 
>>> gain over the existing mechanism like SelfAdjointView?
>>> 
>>> https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointView.html\ 
>>> <https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointView.html/>
>>> 
>>> Do you have some benchmark numbers for your patch?
>>> 
>>> Rasmus
>>> 
>>> On Mon, Oct 5, 2020 at 5:07 PM David Tellenbach 
>>> <[email protected] <mailto:[email protected]>> 
>>> wrote:
>>> Hi Jens,
>>> 
>>> It would be great if you could finish this! I just saw that the patch is 
>>> not accessible anymore, I'll see if I can find it.
>>> 
>>> Best,
>>> David
>>> 
>>>> On 4. Oct 2020, at 21:27, Jens Wehner <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> Thanks David,
>>>> 
>>>> I would probably like to give it a shot to brush up on my template 
>>>> programming skills or lack thereof. 
>>>> 
>>>> Do you have the code somewhere public so I can have a look? If you have 
>>>> time afterwards we can have a chat about the better implementation.
>>>> 
>>>> Cheers Jens
>>>> 
>>>> | Jens Wehner, PhD | eScience Research Engineer | Email: 
>>>> [email protected] 
>>>> <https://outlook.office.com/mail/options/mail/[email protected]> 
>>>> | Tel: +31(0)6 438 666 87 |
>>>> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science 
>>>> Park 140 | 1098 XG Amsterdam | The Netherlands |
>>>> | Twitter <https://twitter.com/eScienceCenter> | LinkedIn 
>>>> <https://www.linkedin.com/company/netherlands-escience-center> | Facebook 
>>>> <https://www.facebook.com/NLeScienceCenter/> | YouTube 
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>>>> <https://esciencecenter.us8.list-manage.com/subscribe/post?u=a0a563ca342f1949246a9f92f&id=31bfc2303d>
>>>>  |
>>>> 
>>>> 
>>>> From: David Tellenbach <[email protected] 
>>>> <mailto:[email protected]>>
>>>> Sent: Sunday, October 4, 2020 0:16
>>>> To: [email protected] <mailto:[email protected]> 
>>>> <[email protected] <mailto:[email protected]>>
>>>> Subject: Re: [eigen] Hermitian matrices
>>>>  
>>>> Hi Jens,
>>>> 
>>>> Yes, I've implemented support for Hermitian matrices as a Google Summer of 
>>>> Code student in 2018 and finishing it is still somewhere on my backlog. 
>>>> However, with today's knowledge the implementation should look quite 
>>>> differently. If you are interested to work on this I'm happy to discuss. 
>>>> Otherwise you will have to wait until I find some time to reimplement it. 
>>>> This won't take me too long but without committing to anything, I can 
>>>> already say that I won't find time before the beginning of 2021.
>>>> 
>>>> Best,
>>>> David
>>>> 
>>>>> On 2. Oct 2020, at 23:30, Jens Wehner <[email protected] 
>>>>> <mailto:[email protected]>> wrote:
>>>>> 
>>>>> I recently discovered that David Tellenbach started/was in the 
>>>>> middle/finished a 
>>>>> 
>>>>> Hermitian matrix class. 
>>>>> http://manao.inria.fr/eigen_tmp/pullrequests/467/ 
>>>>> <http://manao.inria.fr/eigen_tmp/pullrequests/467/>
>>>>> I wanted to know what the status is and if any help is needed to push 
>>>>> that along.
>>>>> 
>>>>> Cheers Jens
>>>>> | Jens Wehner, PhD | eScience Research Engineer | Email: 
>>>>> [email protected] 
>>>>> <https://outlook.office.com/mail/options/mail/[email protected]> 
>>>>> | Tel: +31(0)6 438 666 87 |
>>>>> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science 
>>>>> Park 140 | 1098 XG Amsterdam | The Netherlands |
>>>>> | Twitter <https://twitter.com/eScienceCenter> | LinkedIn 
>>>>> <https://www.linkedin.com/company/netherlands-escience-center> | Facebook 
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>>>>>  |

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